In modern aircraft, it is common to have slats or flaps that may be selectively moved relative to the wing to vary the shape and configuration of the airfoil surface.
In some applications, a motor is operatively arranged to move the flap or slat via a ball screw mechanism. An example of such a ball screw-type mechanism is representatively shown and described in U.S. Pat. No. 4,995,575. However, more recently, efforts have been directed toward using a rack and pinion arrangement to move the flap or slat. In this arrangement, a gear drive mechanism has an outboard pinion (i.e., a non-concentric pinion that is connected to the output shaft of an actuator and that must be supported by is own bearings) that engages a curved rack mounted on the flat or slat. Thus, the driven gear reduction mechanism may be used to selectively rotate the pinion to extend or retract the flap or slat, has desired. Examples of these types of mechanisms are representatively shown and described in U.S. Pat. Nos. 1,917,428, 4,471,928, 4,838,503, 5,544,847 and 6,149,105.
The aggregate disclosures of each of the foregoing references are hereby incorporated by reference insofar as the structure and operation of such prior art mechanisms is concerned.
While these devices have been generally satisfactory in some aspects, they do require separate straddle-mounted bearings to support the pinion. This adds unnecessary weight, which is considered to be at a premium in aircraft applications.
It would, therefore, be generally desirable to provide an improved compact actuator that would afford the capability of providing a combined gear or pinion and a gear reduction mechanism of reduced weight. Such a mechanism would be of particular utility in aircraft applications.